As it is known, recent biological, microbiological and pharmacological applications involve introducing molecules into cells, which is done by introducing the molecules through the cell membranes.
The molecules may be inorganic substances (e.g. drugs) or organic molecules (DNA molecules for example are known to be introduced in cells).
In order to introduce the molecules, the so-called electroporation methods have recently been devised, which are based on the application of electric pulses to the cells in order to produce an electric field that permeabilizes the cell structure enabling the substances to penetrate the cell membrane.
For instance PCT patent application WO01/07583 describes an Electro-poration device wherein an electrical voltage is applied to a substrate comprising cells and a current is flowing through the substrate. The above patent application also proposes to continuously detect the ratio of the current through the substrate to the voltage across the substrate as an indication of the obtained degree of electroporation of the substrate.
Finally, application WO01/07583 proposes to adjust the magnitude of the applied voltage in accordance with changes in the above ratio to achieve a controlled degree of electroporation in the substrate.
However, patent application WO01/07583 does not teach how to use the information related to the above ratio in order to have useful information for controlling the voltage; in other words, WO01/07583 merely discloses the possibility of controlling the voltage based on the detection of the above ratio but does not provide any real indication for creating a working system wherein the control of the voltage is successfully performed.